g-C3N4/ bio–Synthesized Silver Nanoparticle for Fluorometric Bio-sensing of Acetylcholinesterase and Malathion

Abstract Malathion is widely used in agriculture due to their high efficiency as insecticides. They are very toxic hazardous chemicals to both human health and environment even at low concentration. The detection of pesticides (malathion) at the low levels developed by the environmental protection agency (EPA) still remains a challenge. A highly efficient fluorescent biosensor based on g-C3N4/AgNPs for malathion detection is successfully developed by impregnation method. The structural properties of the developed nanocomposites were characterized by using powder X-ray diffraction (XRD) and fourier- transform infrared spectroscopy (FT-IR). The analysis confirmed that there is a strong interfacial interaction between g-C3N4 and AgNPs. The developed sensor immobilizes by acetylcholestrase (AChE). In the absence of malathion, AChE − g-C3N4/AgNCs exhibit high fluorescence intensity. However, the strong interaction of the basic sites to malathion, causes fluorescence quenching via static quenching and Ag form aggregation on the surface of g-C3N4. The experimental parameter such as pH of buffer (pH = 6), concentration of acetylcholine (1 mM) and malathion (500 µM) were optimized. The sensor was also more sensitive with Stern-Volmer quenching constants (KSV) of 3.48x10 3 M -1. The practical use of this sensor for malathion determination in Khat was also demonstrated. The obtained amount of malathion in Khat is 168.8 µM.